Alarm suspend system

ABSTRACT

An alarm suspend system utilizes an alarm trigger responsive to physiological parameters and corresponding limits on those parameters. The parameters are associated with both fast and slow treatment times corresponding to length of time it takes for a person to respond to medical treatment for out-of-limit parameter measurements. Audible and visual alarms respond to the alarm trigger. An alarm silence button is pressed to silence the audible alarm for a predetermined suspend time. The audible alarm is activated after the suspend time has lapsed. Longer suspend times are associated with slow treatment parameters and shorter suspend times are associated with fast treatment parameters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/510,982 filed Jul. 28, 2009 and entitled “Alarm Suspend System,”which claims priority benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/084,615, filed Jul. 29, 2008,titled “Alarm Management System.” All of the above referencedapplications are hereby incorporated by reference in their entiretyherein.

BACKGROUND

Pulse oximetry for measuring constituents of circulating blood hasachieved acceptance in a wide variety of medical applications, includingsurgical wards, intensive care and neonatal units, general wards, homecare, physical training, and virtually all types of monitoringscenarios. A pulse oximeter generally includes a two-wavelength opticalsensor applied to a patient, a monitor for processing sensor signals anddisplaying results and a patient cable electrically interconnecting thesensor and the monitor. The monitor typically provides a numericalreadout of physiological parameters such as oxygen saturation (SpO₂) andpulse rate (PR). Advanced physiological monitors utilize multiplewavelength sensors and enhanced measurement capabilities to providereadouts of additional parameters, such as carboxyhemoglobin (HbCO),methemoglobin (HbMet) and total hemoglobin (Hbt).

Pulse oximeters capable of reading through motion induced noise aredisclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,650,917,6,157,850, 6,002,952, 5,769,785 and 5,758,644; low noise pulse oximetrysensors are disclosed in at least U.S. Pat. Nos. 6,088,607 and5,782,757; all of which are assigned to Masimo Corporation, Irvine,Calif. (“Masimo”) and are incorporated by reference herein.

Physiological monitors and corresponding multiple wavelength opticalsensors are described in at least U.S. patent application Ser. No.11/367,013, filed Mar. 1, 2006 and titled Multiple Wavelength SensorEmitters and U.S. patent application Ser. No. 11/366,208, filed Mar. 1,2006 and titled Noninvasive Multi-Parameter Patient Monitor, bothassigned to Masimo Laboratories, Irvine, Calif. (Masimo Labs) and bothincorporated by reference herein.

Further, physiological monitoring systems that include low noise opticalsensors and pulse oximetry monitors, such as any of LNOP® adhesive orreusable sensors, SofTouch™ sensors, Hi-Fi Trauma™ or Blue™ sensors; andany of Radical®, SatShare™, Rad-9™, Rad-5™, Rad-5v™ or PPO+™ Masimo SET®pulse oximeters, are all available from Masimo. Physiological monitoringsystems including multiple wavelength sensors and correspondingnoninvasive blood parameter monitors, such as Rainbow™ adhesive andreusable sensors and RAD-57™ and Radical-7™ monitors for measuring SpO₂,pulse rate (PR), perfusion index (PI), pleth variability index (PVI),signal quality, HbCO and HbMet among other parameters are also availablefrom Masimo.

SUMMARY OF THE INVENTION

Monitor alarms are triggered by out-of-limit parameters and systemfailures, the latter including monitor or sensor failures or impropersensor placement, to name a few. Alarms can be visual, audible or both.Alarms can also have different levels of priority, which are reflectedin the type of visual and audible alarms. In an embodiment, parametersexceeding limits such as low SpO₂, high HbCO, high HbMet and low andhigh BPM trigger high priority alarms. System failures due to sensoroff, no sensor or defective sensor also trigger high priority alarms.Parameters exceeding limits such as high SpO₂, low and high PI, low andhigh PVI, for example, trigger medium priority alarms. Parametersexceeding limits such as low HbCO and low HbMet along with a system lowbattery indication are examples of low priority alarms.

An audible alarm may be temporarily suspended by pressing an alarmsilence button so as to prevent unnecessary disturbance to the patientand distraction of the caregiver. During alarm suspension, visual alarmsremain active. If an alarm condition persists after a predeterminedalarm suspend period, the audible alarm resumes. The alarm suspendperiod is typically long enough to give a caregiver sufficient time tointervene with appropriate patient treatment yet short enough to ensurethat patient health is not endangered if intervention is ineffective.For conventional pulse oximetry, an alarm suspend may be, for example, amaximum of 120 seconds.

Alarm suspension on advanced blood parameter monitors is problematic.With conventional pulse oximetry, treatment for abnormal parametermeasurements can be quickly applied and a patient response is typicallyfast. For example, a treatment for low oxygen saturation is theapplication of an oxygen mask or an increase in oxygen flow. Bycontrast, the duration of treatment for parameters measured by advancedmonitors is highly dependent on the alarm-triggering parameter. Forexample, the treatment for high methemoglobin is the injection ofmethylene blue, and the patient response to such an injection is slow.When patient treatment time exceeds the maximum alarm suspend period, anaudible alarm will constantly reactivate. Thus, a single alarm suspendduration for all parameters is inadequate to cope with the manydifferent types of parameters measured by advanced monitors.

One aspect of an alarm suspend system for silencing the alarms is analarm trigger responsive to any of various parameters and predeterminedlimits corresponding to the parameters, where the parameters arepartitioned according to treatment time, i.e. the relative length oftime it takes for a person to respond to medical treatment for aparameter measurement outside of the predetermined limits. An audiblealarm is responsive to the alarm trigger. An alarm silence button isactuated so as to suspend the audible alarm. A timer tracks the durationof the suspended alarm and is initiated by actuation of an alarm silencebutton. The timer retriggers the audible alarm after the timed durationhas lapsed/expired. In an embodiment, a long duration suspend time isassociated with slow treatment parameters and a short duration suspendtime is associated with fast treatment parameters. Fast treatmentparameters may include, for example, parameters relating to normal bloodhemoglobin constituents and slow treatment parameters may includeparameters relating to abnormal blood hemoglobin constituents.

In various embodiments, a short duration suspend time is less than orequal to about two minutes and a long duration suspended time is greaterthan about two minutes. A default duration associated with the fasttreatment parameters is about two minutes and a default durationassociated with the slow treatment parameters is about fifteen minutes.The alarm suspend system may also have an alarm suspend overrideresponsive to a predetermined unit change in the parameter triggering asuspended alarm. The override results in reactivation of the suspendedalarm. A physiological monitor having an alarm suspend system may alsohave a pop-up window that appears on the monitor display in response toactuation of the silence button, where the pop-up window presents achoice of alarm suspend durations.

Another aspect of an alarm suspend system is a partition of measuredparameters into at least a first group and a second group. An audiblealarm is triggered if at least one parameter is outside of predeterminedlimits. The audible alarm is suspended in response to a silence request.A first duration is associated with the first group and a secondduration is associated with the second group. The audible alarm isreactivated after at least one of the first duration and the secondduration. The first duration may be set so as to generally correspond toa first range of treatment times for the first group of parameters.Likewise, the second duration may be set so as to generally correspondto a second range of treatment times for the second group of parameters,where the first range of treatment times and the second range oftreatment times are non-overlapping.

In various embodiments, suspended audible alarms are overridden if thetriggering parameter has greater than a predetermined unit change beforethe suspended alarm expires according to either the first duration orthe second duration. The first and second groups are defined in relationto normal hemoglobin measurements abnormal hemoglobin measurements,respectively. The first duration is set to be less than or equal to twominutes and the second duration is set to be greater than two minutes,with default durations of about two minutes corresponding to the firstgroup and about fifteen minutes corresponding to the second group. In anembodiment, a pop-up window for a monitor display is constructed and thefirst duration and the second duration are selected from a range ofdurations presented within the pop-up window.

A further aspect of an alarm suspend system deactivates an audible alarmfor one of a short duration and a long duration according to thealarm-triggering parameter. A first group of parameters is associatedwith the short duration and a second group of parameters is associatedwith the long duration. The first group and the second group arepartitioned according to a fast treatment time and a short treatmenttime associated with the parameters. An override reactivates the audiblealarm if the trigger parameter changes more than a predetermine amountduring the corresponding duration. In various embodiments, the firstgroup comprises parameters related to the measurement of normalhemoglobin and the second group comprises parameters related to themeasurement of abnormal hemoglobin. The long duration is greater thanabout 120 seconds and the short duration is less than or equal to about120 seconds. A pop-up window for the display allows selection of thelong duration and the short duration in response to the silence button.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a physiological measurement systemutilizing an alarm suspend system;

FIG. 2 is a detailed block diagram of a physiological measurement systemutilizing an alarm suspend system;

FIG. 3 is a flow diagram of an alarm suspend system embodiment;

FIG. 4 is a state diagram of an alarm suspend system embodiment; and

FIG. 5 is an illustration of an alarm suspend pop-up window.

DETAILED DESCRIPTION

FIG. 1 illustrates a physiological measurement system 100 that utilizesan alarm suspend system. The physiological measurement system 100 has anoninvasive sensor 105 attached to a tissue site 10, a physiologicalmonitor 101, and an interface cable 109 interconnecting the monitor 101and the sensor 105. The physiological measurement system 100 mayincorporate pulse oximetry in addition to advanced features, such as amultiple wavelength sensor and advanced processes for determiningphysiological parameters other than or in addition to those of pulseoximetry, such as carboxyhemoglobin, methemoglobin and total hemoglobin,as a few examples.

The monitor 101 has a front panel 110 providing a display 120, touchkeys 130, controls 140, a speaker 150, a sensor port 160 and statusindicators 170. The display 120 shows parameter readouts, limits andwaveforms among other items. The display 120 also has touch key icons122 that indicate touch key 130 functions. The speaker 150 provides anaudible alarm in response to physiological measurements that violatepreset conditions, such as an out-of-limit parameter, as well as systemfailures, such as a low battery condition. The controls 140 include analarm silence button 144 that is pressed to temporarily suspendout-of-limit parameter alarms and system alarms, such as low battery.The display 120 provides visual alarms, which include a bell-shapedalarm status indicator 124 that illuminates during an alarm conditionand parameter readouts 210 and limits 220 that flash when parameters areout-of-limit. Status indicators 170 also provide visual alarms. Whenthere are multiple alarm conditions, the parameter displays 202 indicateparameters with the highest alarm priority. Touch keys 130 andcorresponding icons 122 include an alarm menu access button for settingalarm conditions, such as high or low alarm limits for SpO₂, HbCO,HbMet, PR and PI. The alarm silence button 144 is pressed to temporarilysuspend audible alarms. Advantageously, an alarm suspend system providesa parameter-dependent variation in the alarm suspend duration, asdescribed below, utilizing a common silence button or other suspendinitiator.

FIG. 2 illustrates a physiological measurement system 200 including aphysiological monitor 201, a sensor 205 and an interface cable 209. Thesensor 205 is attached to a tissue site, such as a finger 10, andincludes a plurality of emitters 206 irradiating the tissue site 10 withmultiple wavelengths of light. The sensor 205 also includes one or moredetectors 208 capable of detecting the light after attenuation by thetissue site 10. The sensor 205 transmits optical radiation atwavelengths other than or including the red and infrared wavelengthsutilized in pulse oximeters. The monitor 201 inputs a correspondingsensor signal 211 and determines the relative concentrations of bloodconstituents other than or in addition to the “normal” blood hemoglobinconstituents HbO₂ and Hb, including “abnormal” blood hemoglobinconstituents HbCO, HbMet and blood related parameters such as fractionaloxygen saturation, total hemoglobin and blood glucose to name a few.

As shown in FIG. 2, the monitor 201 has a front-end signal conditioner210, an ND converter 220, emitter drivers 230, D/A converters 240 and adigital signal processor (“DSP”) 250. In general, the emitter drivers230 convert digital control signals, via the D/A converters 240, intoanalog drive signals capable of driving the sensor emitters 206. Thefront-end signal conditioner 210 converts, via the ND converter 220,composite analog intensity signal(s) from light sensitive detector(s)208 into digital data input to the DSP 250. The emitter drivers 230 andfront-end signal conditioner 210 communicate with the sensor 205 via theinterface cable 209.

Also shown in FIG. 2, the monitor 201 has an instrument manager 260 anda user interface 280. The user interface 280 includes one or moredisplays 282, alarms 284 and user input/output (I/O) 286. The instrumentmanager 260 communicates with the DSP 250 to receive parameter data andto present that data on the display 282. The instrument manager 260 mayalso store and display historical or trending data related to one ormore of the measured parameters or combinations of the measuredparameters. The instrument manager 260 also controls audible and visualalarms and indicators 284. The instrument manager 260 responds touser-actuated keys and communicates with external devices via variousI/O ports 286. Further, the instrument manager 260 executes alarmsuspend firmware 270 so as to respond to an alarm silence button press288, as described in detail with respect to FIGS. 3-4.

FIG. 3 generally illustrates an alarm suspend system 300. Alarm triggersinclude system failures 338 and out-of-limit parameters 318. Triggeredalarms 340 may be audible, visual or both, and may vary according topriority 342. Audible alarms may be generated by a monitorfront-panel-mounted speaker 150 (FIG. 1) and may vary in loudness, pitchand sound pattern. Visual alarms may include parameter labels, parameternumerics, symbols and status lights, which can flash and vary in color.

As shown in FIG. 3, measured parameters 312 are compared 310 to defaultor user-specified limits 314. An out-of-limit condition 318 triggers analarm 340. An alarm suspend 328 is user-initiated by a silence request322. This may be a press of a silence button 144 (FIG. 1) on a monitorfront panel 110 (FIG. 1). In an embodiment, the alarm suspend 328silences audible alarms and modifies the display of visual alarms. Thealarm suspend 328 is based on a timer 320, which ends the alarm suspend328 after a predetermined duration 324. The duration 324 may be afunction of the out-of-limit parameter 312. In an advantageousembodiment, the duration 324 relates to, or is a function of, thetreatment time for the alarm-triggering parameter so as to avoidnuisance alarms while maintaining alarm integrity.

FIG. 4 illustrates an alarm suspend embodiment 400 that operatesindependently for each measured parameter that can trigger an alarm. Analarm is initially off 410. The alarm remains off as long as theparameter is within its set limits 412. If a parameter is measuredoutside of its set limits 414, an alarm is triggered 420. The alarm mayaudible, visual or both audible and visual. A user can request tosilence the alarm by pressing an alarm silence button 144 (FIG. 1), forexample. The silence request 422 suspends the alarm 430 which turns offaudible alarms but, in an embodiment, does not deactivate visual alarms.The audible alarm remains suspended 430 for a predetermined duration432. When the suspend duration has passed, the alarm suspend expires 434and audible alarms are once again activated 420. The alarm remains on428 until the triggering parameter is within limits 424 or a user onceagain requests silence 422. The alarm suspend 430 deactivates if themeasured parameter becomes within limits 438, such as when the patientcondition improves, or if no physiological data is detected 439, such asno sensor, sensor off, no cable or malfunctioning sensor situations, toname a few. Also, if the measured parameter changes during the alarmsuspend 430 by a sufficient out-of-limit amount, an override 436reactivates the audible alarms 420.

In an alarm suspend system embodiment, parameters are classifiedaccording to the typical time it takes for medical treatment totransition an out-of-limit measurement to a within-limit measurement.Suspend durations 324 (FIG. 3) are set accordingly. For example, in atwo-tier embodiment, relatively slow treatment parameters, such asHbMet, HbCO, Hbt and PVI, are assigned relatively long suspenddurations. Similarly, relatively fast treatment parameters, such as SpO₂and PR, are assigned relatively short suspend durations. In anembodiment, the alarm suspend duration is adjustable for each individualparameter, including 2, 5, 10, 15, 20, 25 and 30 minutes for slowtreatment parameters, with a default of 15 minutes; and 30, 60, 90 and120 seconds for fast treatment parameters, with a default of 120seconds. These alarm features are only active when alarm limits havebeen set. Other alarm features apply to both slow treatment and fasttreatment parameters. For example, an alarm delay of 0, 5, 10 or 15seconds applies to all enabled parameters.

In an embodiment, an override 436 occurs if slow treatment parameterssuch as HbCO, HbMet or PVI increase or Hbt decreases by a certain unitchange during the alarm suspend duration. The unit change is adjustablefor each parameter, such as from 1-15 in increments of 1. TABLE 1 showsa default embodiment of override unit changes for these parameters.

TABLE 1 Override Unit Changes for Selected Parameters Parameter UnitChange Direction HbCO 5 Increase HbMet 2 Increase Hbt 2 Decrease PVI OFFIncrease

FIG. 5 illustrates an alarm suspend window 500 that provides a “pop-up”display so that a monitor user may manually enter an alarm suspendduration. The alarm suspend window 500 appears as a portion of a monitordisplay 501, such as the front panel display 120 (FIG. 1) describedabove. The pop-up window 500 responds to a suspend request, such as asilence button 144 (FIG. 1) press. The alarm suspend window 500 has awindow identifier 502 and one or more parameter subsections 510, 520.Each parameter subsection 510, 520 has a parameter identifier 512, 522and corresponding suspend duration options 514, 524. In an embodiment,specific suspend times are selected via monitor touch keys 130 (FIG. 1)as guided by corresponding touch key icons 560. Selected suspend timesare highlighted or otherwise identified and entered, also via a touchkey 130 (FIG. 1). In an alternative embodiment, the monitor display is atouch screen and alarm suspend times are directly entered by a fingerpress on a specific duration “virtual button” 514, 524. Once one or moresuspend durations are entered, the pop-up window 500 disappears from thedisplay 501. The alarm suspend window 500 advantageously allows a userto quickly choose an appropriate alarm suspend duration for thesituation at hand, rather than relying on a predetermined or defaultduration.

An alarm suspend system is described above with respect to alarmstriggered by measured parameters and limits associated with thosemeasured parameters. Limits may correspond to levels of a measuredparameter, such as a percentage oxygen saturation to name but oneexample. Limits may also correspond to trends of a measured parameter,such as a rate-of-change of oxygen saturation, for example. Limits mayalso correspond to patterns in a measured parameter or a comparison ofone measured parameter with another measured parameter, as furtherexamples.

An alarm suspend system is described above with respect to a two-tiergrouping of parameters, such as slow treatment and fast treatmentparameters and alarm suspend durations associated with those groups.Groupings of parameters with respect to alarm suspend durations may bemulti-tier, such as slow, medium and fast treatment parameters, to namebut one example.

An alarm suspend system has been disclosed in detail in connection withvarious embodiments. These embodiments are disclosed by way of examplesonly and are not to limit the scope of the claims that follow. One ofordinary skill in the art will appreciate many variations andmodifications.

1. A noninvasive optical based physiological measurement systemcomprising: a plurality of light emitting diodes configured to transmita plurality of wavelengths of light onto a tissue site of a patient; atleast one detector configured to measure an indication of the pluralityof wavelengths of light after attenuation by tissue of the patient andoutput a signal indicative of the attenuated light; one or moreprocessors configured to receive the detector output signal and todetermine a plurality of different physiological measurements, the oneor more processors further configured to determine if an alarm thresholdhas been met and activate an alarm; a speaker associated with the one ormore processors, the speaker configured to generate an audible signal inresponse to the alarm activated by the one or more processors; and asilence button associated with the one or more processors; wherein, whenthe alarm is activated for at least one of the plurality of differentphysiological measurements and the silence button is activated by auser, the one or more processors deactivate the alarm for a period oftime, the period of time being different for each differentphysiological measurement of the plurality of different physiologicalmeasurements.
 2. The noninvasive optical based physiological measurementsystem of claim 1, wherein the physiological measurements comprise oneor more of oxygen saturation, pulse rate, carboxyhemoglobin,methemoglobin and total hemoglobin.
 3. The noninvasive optical basedphysiological measurement system of claim 1, wherein the period of timeis related to an expected course of treatment for the activated alarm.4. An alarm suspend method comprising: measuring a plurality ofphysiological parameters using a patient monitoring device including aprocessor; triggering an audible alarm if at least one parameter isoutside of predetermined limits; suspending the audible alarm inresponse to a silence request; associating a duration with each of theplurality of physiological parameters, wherein at least a first durationassociated with a first physiological parameter is different than asecond duration associated with a second physiological parameter; andreactivating the audible alarm after the duration associated with the atleast one parameter outside the predetermined limits has passed.
 5. Thealarm suspend method according to claim 4 further comprising setting theduration to correspond with a range of treatment times associated withthe at least one parameter outside the predetermined limits has passed.6. The alarm suspend method according to claim 4 further comprisingoverriding the suspended audible alarm if the triggering parameter hasgreater than a predetermined unit change before the duration has passed.7. The alarm suspend method according to claim 4 wherein at least oneduration is about two minutes.
 8. The alarm suspend method according toclaim 4 wherein at least one duration duration is about fifteen minutes.9. The alarm suspend method according to claim 4 further comprising:constructing a pop-up window for a monitor display; and selecting theduration from a range of durations presented within the pop-up window.10. The alarm suspend method according to claim 4 further comprisingtriggering the audible alarm if no parameters are found duringmeasuring.
 11. The alarm suspend method according to claim 4, whereinthe plurality of physiological parameters are measured using multiplewavelength sensing.
 12. The alarm suspend method according to claim 6,wherein the predetermined unit change is adjustable for eachphysiological parameter.
 13. A physiological measurement systemcomprising: a sensor configured to attach to a patient so as to transmitoptical radiation into a tissue site and generate a sensor signalresponsive to the optical radiation after attenuation by pulsatile bloodflow within the tissue site; a monitor in communications with the sensorso as to measure a plurality of physiological parameters responsive tothe sensor signal; a display mounted on the monitor that displays themeasured parameters along with visual alarms associated with themeasured parameters; a speaker mounted on the monitor that generates anaudible alarm triggered by at least one of the parameters; a silencebutton mounted on the monitor that, when actuated, initiates a silencerequest for the monitor to suspend the audible alarm; and an alarmsuspend system that deactivates the audible alarm for a parameterspecific duration according to the alarm-triggering parameter.
 14. Thephysiological measurement system according to claim 13 wherein the alarmsuspend system comprises: a first group of parameters associated with ashort duration; a second group of parameters associated with a longduration; the first group and the second group partitioned according toa fast treatment time and a short treatment time associated with theparameters.
 15. The physiological measurement system according to claim13 further comprising an override that reactivates the audible alarm ifthe triggered parameter changes more than a predetermine amount duringthe corresponding duration.
 16. The physiological measurement systemaccording to claim 14 wherein the first group comprises parametersrelated to the measurement of normal hemoglobin and the second groupcomprises parameters related to the measurement of abnormal hemoglobin.17. The physiological measurement system according to claim 14 whereinthe long duration is greater than about 120 seconds.
 18. Thephysiological measurement system according to claim 14 wherein the shortduration is less than or equal to about 120 seconds.
 19. Thephysiological measurement system according to claim 14 furthercomprising a pop-up window for the display that allows selection of thelong duration and the short duration in response to the silence button.20. The physiological measurement system according to claim 14 furthercomprising: a third group of parameters associated with a high priority;a fourth group of parameters associated with a low priority; the thirdgroup and the fourth group partitioned according to a high medicalpriority and a low medical priority associated with the parameters; andwherein the visual alarms associated with the third group are displayedwhen both the visual alarms associated with the third group and thefourth group are to be displayed.